Coupling a high-contrast imaging instrument to a high-resolution spectrograph has the potential to enable the most detailed characterization of exoplanet atmospheres, including spin measurements and Doppler mapping. The high-contrast imaging system serves as a spatial filter to separate the light from the star and the planet while the high-resolution spectrograph acts as a spectral filter, which differentiates between features in the stellar and planetary spectra. The Keck Planet Imager and Characterizer (KPIC) located downstream from the current W. M. Keck II adaptive optics (AO) system will contain a fiber injection unit (FIU) combining a high-contrast imaging system and a fiber feed to Keck’s high resolution infrared spectrograph NIRSPEC. Resolved thermal emission from known young giant exoplanets will be injected into a single-mode fiber linked to NIRSPEC, thereby allowing the spectral characterization of their atmospheres. Moreover, the resolution of NIRSPEC (R = 37,500) is high enough to enable spin measurements and Doppler imaging of atmospheric weather phenomenon. The module will be integrated and tested at Caltech before being transferred to Keck in 2018.
General relativity can be tested in the strong gravity regime by monitoring stars orbiting the supermassive black hole at the Galactic Center with adaptive optics. However, the limiting source of uncertainty is the spatial PSF variability due to atmospheric anisoplanatism and instrumental aberrations. The Galactic Center Group at UCLA has completed a project developing algorithms to predict PSF variability for Keck AO images. We have created a new software package (AIROPA), based on modified versions of StarFinder and Arroyo, that takes atmospheric turbulence profiles, instrumental aberration maps, and images as inputs and delivers improved photometry and astrometry on crowded fields. This software package will be made publicly available soon.
The Keck II Laser Guide Star (LGS) Adaptive Optics (AO) System was upgraded from a dye laser to a TOPTICA/MPBC Raman-Fibre Amplification (RFA) laser in December 2015. The W. M. Keck Observatory (WMKO) has been operating its AO system with a LGS for science since 2004 using a first generation 15 W dye laser. Using the latest diode pump laser technology, Raman amplification, and a well-tuned second harmonic generator (SHG), this Next Generation Laser (NGL) is able to produce a highly stable 589 nm laser beam with the required power, wavelength and mode quality. The beam’s linear polarization and continuous wave format along with optical back pumping are designed to improve the sodium atom coupling efficiency over previously operated sodium-wavelength lasers. The efficiency and operability of the new laser has also been improved by reducing its required input power and cooling, size, and the manpower to operate and maintain it.
The new laser has been implemented on the telescope’s elevation ring with its electronics installed on a new Nasmyth sub-platform, with the capacity to support up to three laser systems for future upgrades. The laser is projected from behind the telescope’s secondary mirror using the recently implemented center launch system (CLS) to reduce LGS spot size. We will present the new laser system and its performance with respect to power, stability, wavelength, spot size, optical repumping, polarization, efficiency, and its return with respect to pointing alignment to the magnetic field. Preliminary LGSAO performance is presented with the system returning to science operations. We will also provide an update on current and future upgrades at the WMKO.
The sky coverage and performance of Laser Guide Star (LGS) adaptive optics (AO) systems is limited by the Natural Guide Star (NGS) used for low order correction (tip-tilt and defocus modes). This limitation can be reduced by measuring image motion of the NGS in the near-infrared where it is partially corrected by the LGS AO system and where stars are generally several magnitudes brighter than at visible wavelengths. We have integrated a Near-InfraRed Tip-Tilt Sensor (NIRTTS) with the Keck I telescopes LGS AO system. The sensor is a H2RG-based near-infrared camera with 0.05 arcsecond pixels. Low noise at high sample rates is achieved by only reading a small region of interest, from 2x2 to 16x16 pixels, centered on an NGS anywhere in an 100 arc second diameter field. The sensor operates at either Ks or H-band using light reflected by a choice of dichroic beam-splitters located in front of the OSIRIS integral field spectrograph. The implementation of the NIRTTS involved modifications to the AO bench, real-time control system, higher-level controls and operations software. NIRTTS is nearly ready for science operation in shared-risk mode. We are also implementing a number of enhancements to the NIRTTS system which involve substantial changes to the operations software. This work presents an update of the work performed since the NIRTTS system was reported in Ref. 1 and Ref. 2.
On March 2015 an L'-band vortex coronagraph based on an Annular Groove Phase Mask made up of a diamond sub-wavelength grating was installed on NIRC2 as a demonstration project. This vortex coronagraph operates in the L' band not only in order to take advantage from the favorable star/planet contrast ratio when observing beyond the K band, but also to exploit the fact that the Keck II Adaptive Optics (AO) system delivers nearly extreme adaptive optics image quality (Strehl ratios values near 90%) at 3.7μm. We describe the hardware installation of the vortex phase mask during a routine NIRC2 service mission. The success of the project depends on extensive software development which has allowed the achievement of exquisite real-time pointing control as well as further contrast improvements by using speckle nulling to mitigate the effect of static speckles. First light of the new coronagraphic mode was on June 2015 with already very good initial results. Subsequent commissioning nights were interlaced with science nights by members of the VORTEX team with their respective scientific programs. The new capability and excellent results so far have motivated the VORTEX team and the Keck Science Steering Committee (KSSC) to offer the new mode in shared risk mode for 2016B.
Laser Guide Star (LGS) facilities for adaptive optics (AO) have been in routine scientific operation on the Keck II and Keck I telescopes since 2004 and 2012, respectively. Two upgrades are currently in process for the Keck II LGS facility: moving the launch of the laser from the side of the Keck telescope to behind the secondary mirror and replacing the existing dye laser with a Raman-fiber amplifier (RFA) laser. Both of these upgrades are on the path to a multi-LGS facility for Keck’s next generation AO (NGAO) system. We will discuss the performance and operations experience with the existing LGS facilities with an emphasis on the newer Keck I LGS facility, the recently implemented Keck II center launch system and its initial on-sky results, the progress on the design and implementation of the new fiber laser, and the plans for a multi-LGS facility for NGAO.
The increasing availability of sensors that can image in the 1 to 5 μm region has allowed for systems to be developed that utilize the full spectrum. Current mid-wave infrared (MWIR) systems have typically only imaged in the 3 to 5 μm region, but the new detectors allow imaging in the short-wave infrared (SWIR) and MWIR bands on the same image plane. Night Vision and Electronic Sensors Directorate (NVESD) had a requirement to design and build a multiple field of view (FOV) optical system that could image the 1 to 5 μm spectral band utilizing a single, cooled infrared detector. The primary challenge of designing this particular optical system was to get the 1 to 2 (SWIR) µm band to focus at the same image plane as the 3 to 5 (MWIR) µm band in all FOVs. A three-FOV broadband optical system that can image the 1 to 5 μm band on the same image plane was designed and built. Several optical concepts were looked at, and it was decided that a combination of a reflective afocal and refractive imager was the best way to meet the system requirements. The use of a catadioptric system with a single focal plane that images in the 1 to 5 μm spectrum reduces the size of the system and provides the user with see-spot capability.
The increasing availability of sensors that can image in the 1-5 micron region has allowed for systems to be developed
that utilize the full spectrum. Past MWIR systems have typically only imaged in the 3-5 micron region, but the new
detectors allow imaging in the SWIR and MWIR bands with the same system. The use of a single FPA reduces SWAP
and allows the user to see laser rangefinder and laser designator wavelengths. NVESD and Axsys have designed and
built a SWIR/MWIR optical system that images in the 1-5 micron band. The optical system utilizes a cooled infrared
detector that images in the 3-5 micron band as well as 1.04 - 1.08 and 1.54 microns without having to refocus the system
to see the SWIR wavelengths. This provided an optical challenge to design a system that would image from 1-5 microns
on the same detector. A combination reflective/refractive design was chosen in order to minimize packaging and meet
the different FOV requirements. This paper discusses the design and development of a multi-FOV optical system with
the capability to image across the 1-5 micron spectral band utilizing a combination of reflective and refractive